Energy harvesting brake system

ABSTRACT

An energy harvesting brake system may comprise a shaft, a roller cylinder, and a piezoelectric material. The roller cylinder may be configured to rotate relative to the shaft in response to a target moving relative to a platform. The piezoelectric material may be in operable communication with the shaft and the roller cylinder such that relative rotational motion between the shaft and the roller cylinder causes cyclic stress in the piezoelectric material thereby generating electrical energy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of India PatentApplication No. 202041010914 filed on Mar. 13, 2020 and entitled “ENERGYHARVESTING BRAKE SYSTEM,” which is hereby incorporated by reference inits entirety.

FIELD

The present disclosure relates generally to cargo handling systems and,more particularly, energy harvesting brake systems for cargo handlingsystems.

BACKGROUND

Cargo handling systems for aircraft typically include various tracks androllers disposed on a cargo deck that spans the length of a cargocompartment. Cargo may be loaded from an entrance of the aircraft andtransported by the cargo system to forward or aft locations, dependingupon the configuration of the aircraft. Cargo handling systems, such as,for example, those used on aircraft for transport of heavy containerizedcargo or pallets, also referred to herein as unit load devices (ULDs),typically include roller trays containing transport rollers that supportand transport the containerized cargo or pallets. Motor driven rollersare typically employed in these systems. In certain aircraft, aplurality of motor driven power drive units (PDUs) is used to propel thecontainers or pallets within the cargo compartment. This configurationfacilitates transportation of the containers or pallets within the cargocompartment by one or more operators or agent-based systems controllingoperation of the PDUs.

Unwanted movement of ULDs during loading and unloading may present asafety risk to operators or related loading personnel or result indamage to an aircraft cargo compartment. Braking mechanisms are thusinstalled within the cargo handling system to help protect loadingpersonnel and the aircraft from possible damage during loading andunloading due to unwanted movement. A typical braking mechanism includesa braking caster, which may have a rotating element that protrudes abovea conveyor plane (e.g., the plane upon which the ULDs traverse the cargodeck) and is typically installed near the cargo door. The rotatingelement of the braking caster is configured to decelerate or stop a ULD,but allow travel when the ULD is manually or power driven over the cargodeck.

The rotating element typically has a preset braking load selected for amaximum weight of a loaded ULD at a maximum angle of the cargo deck orthe conveyor plane. Because of the maximum settings, the braking loadmay be too powerful to allow the rotating element to roll under lightloads. The rotating element often includes a friction material thatsurrounds the outer surface of a cylindrical roller. In instances wherethe load applied to the rotating element is not sufficient to overcomethe braking load, the ULD may skid over the roller, wear away thefriction material and create a flat spot on the roller.

The power demands of cargo handling systems and aircrafts in general areincreasing due to, for example, the use of smart electric systems and anincreased number of active sensors, which draw power throughout a flightcycle. Conventional power generation may add more weight to the systemwhich may reduce the systems performance and efficiency.

SUMMARY

An energy harvesting brake system is disclosed herein. In accordancewith various embodiments, the energy harvesting brake system maycomprise a shaft, a roller cylinder, and a piezoelectric material. Theroller cylinder may be configured to rotate relative to the shaft inresponse to a target moving relative to a platform. The energyharvesting brake system being disposed in the platform. Thepiezoelectric material may be in operable communication with the shaftand the roller cylinder such that relative rotational motion between theshaft and the roller cylinder causes cyclic stress in the piezoelectricmaterial thereby generating electrical energy.

In various embodiments, the energy harvesting brake system may furthercomprise a guide plate and a slider disk. The guide plate may beconfigured to rotate about the shaft and may include a roller. Theslider disk may have a first axial facing surface defining a slider disktrough and a slider disk peak. The slider disk may be configured totranslate axially on the shaft in response to the roller interactingwith the slider disk trough and the slider disk peak. The piezoelectricmaterial may be configured to deform in response to translation of theslider disk on the shaft.

In various embodiments, the guide plate may comprise a radially outwardextending protrusion configured to engage the roller cylinder. Theslider disk may be rotationally stationary with respect to the shaft.

In various embodiments, a brake stack may be located around the shaft.The brake stack may include a stator plate, a rotor plate, and a rollerand roller cage element located axially between the stator plate and therotor plate. In various embodiments, the stator plate may comprise thepiezoelectric material.

In various embodiments, a flange may extend radially outward from theshaft. The flange may have a second axial facing surface oriented towardthe first axial facing surface. The second axial facing surface maydefine a flange trough and a flange peak.

In various embodiments, a wire may be electrically coupled to thepiezoelectric material. In various embodiments, the wire may be locatedin a channel defined by the shaft.

In various embodiments, a brake stack may be located around the shaft.The brake stack may comprise a first stator plate and a first rotorplate. The first stator plate may include a first radially inwardextending protrusion located in a first slot defined by the shaft. Thefirst rotor plate may include a first radially outward extendingprotrusion located in a second slot defined by the roller cylinder. Thebrake stack may further comprise a second stator plate and a secondrotor plate. The second stator plate may include a second radiallyinward extending protrusion located in the first slot defined by theshaft. The second rotor plate may include a second radially outwardextending protrusion located in the second slot defined by the rollercylinder. A first roller and roller cage element may be located axiallybetween the first stator plate and the first rotor plate. A secondroller and roller cage element may be located axially between the secondstator plate and the second rotor plate.

In various embodiments, the first stator plate may comprise thepiezoelectric material, and the second stator plate may comprise asecond piezoelectric material.

In various embodiments, a wire may be electrically coupled to thepiezoelectric material and the second piezoelectric material. The wiremay be located in a channel defined by the shaft.

A method of harvesting electrical energy while braking is also disclosedherein. In accordance with various embodiments, the method may comprisemoving a target relative to a platform having an energy harvesting brakesystem disposed therein, rotating a roller cylinder of the energyharvesting brake system with the movement of the target, cyclicallystressing a piezoelectric material disposed in the energy harvestingbrake system with the rotation of the roller cylinder, and generatingelectrical energy with the cyclical stressing.

In various embodiments, the method may further comprise braking movementof the target relative to the platform. In various embodiments, theenergy harvesting brake system may comprise a shaft, the rollercylinder, the piezoelectric material, a guide plate configured to rotateabout the shaft, and a slider disk configured to translate axially onthe shaft in response to rotation of the guide plate about the shaft.The piezoelectric material may be configured to deform in response toaxial translation of the slider disk.

An energy harvesting system is also disclosed herein. In accordance withvarious embodiments, the energy harvesting system may comprise a firstenergy storage device and an energy harvesting brake system electricallycoupled to the first energy storage device. The energy harvesting brakesystem may include a shaft, a roller cylinder, and a piezoelectricmaterial. The roller cylinder may be configured to rotate relative tothe shaft. The piezoelectric material may be in operable communicationwith the shaft and the roller cylinder such that relative rotationalmotion between the shaft and the roller cylinder causes cyclic stress inthe piezoelectric material thereby generating electrical energy.

In various embodiments, the energy harvesting brake system may furthercomprise a guide plate configured to rotate about the shaft and a sliderdisk configured to translate axially on the shaft in response torotation of the guide plate about the shaft. the piezoelectric materialmay be configured to deform in response to axial translation of theslider disk.

In various embodiments, a voltage amplification circuit may beelectrically coupled between the piezoelectric material and the firstenergy storage device.

In various embodiments, a cargo handling component may be configured toreceive electrical energy from the first energy storage device. Invarious embodiments, the cargo handling component may comprise at leastone of a sensor, a light, or a second energy storage device.

In various embodiments, the energy harvesting brake system may furthercomprise a flange extending radially outward from the shaft. The flangemay have an axial facing surface defining a flange trough and a flangepeak.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated hereinotherwise. These features and elements as well as the operation of thedisclosed embodiments will become more apparent in light of thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the following detailed description andclaims in connection with the following drawings. While the drawingsillustrate various embodiments employing the principles describedherein, the drawings do not limit the scope of the claims.

FIG. 1A illustrates an aircraft being loaded with cargo, in accordancewith various embodiments;

FIG. 1B illustrates a portion of a cargo handling system, in accordancewith various embodiments;

FIGS. 2A and 2B illustrate an assembled view and an exploded view,respectively, of an energy harvesting brake system, in accordance withvarious embodiments;

FIG. 3A illustrates a cross sectional view of an energy harvesting brakesystem taken along the line 3A-3A in FIG. 2A, in accordance with variousembodiments;

FIG. 3B illustrates an exploded view of a brake assembly of an energyharvesting brake system, in accordance with various embodiments;

FIG. 3C illustrates a perspective view of a shaft of a brake assemblyfor an energy harvesting brake system, in accordance with variousembodiments;

FIG. 3D illustrates a perspective view of a slider disk of a brakeassembly for an energy harvesting brake system, in accordance withvarious embodiments;

FIGS. 3E and 3F illustrates a perspective view and a side view,respectively, of a guide plate with rollers of a brake assembly for anenergy harvesting brake system, in accordance with various embodiments;

FIGS. 4A and 4B illustrate an energy harvesting brake system in a stateof minimum brake force, in accordance with various embodiments;

FIGS. 4C and 4D illustrate an energy harvesting brake system in a stateof maximum brake force, in accordance with various embodiments;

FIG. 5 provides graphs illustrating brake force versus roller cylinderrotation for an energy harvesting brake system, in accordance withvarious embodiments;

FIG. 6 illustrates an energy harvesting system including an energyharvesting brake system, in accordance with various embodiments; and

FIG. 7 illustrates a method of harvesting electrical energy whilebraking, in accordance with various embodiments.

DETAILED DESCRIPTION

The following detailed description of various embodiments herein makesreference to the accompanying drawings, which show various embodimentsby way of illustration. While these various embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosure, it should be understood that other embodiments may berealized and that changes may be made without departing from the scopeof the disclosure. Thus, the detailed description herein is presentedfor purposes of illustration only and not of limitation. Furthermore,any reference to singular includes plural embodiments, and any referenceto more than one component or step may include a singular embodiment orstep. Also, any reference to attached, fixed, connected, or the like mayinclude permanent, removable, temporary, partial, full or any otherpossible attachment option. Additionally, any reference to withoutcontact (or similar phrases) may also include reduced contact or minimalcontact. It should also be understood that unless specifically statedotherwise, references to “a,” “an” or “the” may include one or more thanone and that reference to an item in the singular may also include theitem in the plural. Further, all ranges may include upper and lowervalues and all ranges and ratio limits disclosed herein may be combined.

With reference to FIG. 1A, an aircraft 10 is illustrated. In accordancewith various embodiments, aircraft 10 includes a cargo deck 12 locatedwithin a cargo compartment 14 of aircraft 10. The aircraft 10 maycomprise a cargo load door 16 located, for example, at one side of afuselage structure of the aircraft 10. A unit load device (ULD) 20, inthe form of a container or pallet, for example, may be loaded throughthe cargo load door 16 and onto the cargo deck 12 of the aircraft 10 or,conversely, unloaded from the cargo deck 12 of the aircraft 10. Ingeneral, ULDs are available in various sizes and capacities, and aretypically standardized in dimension and shape. Once loaded with itemsdestined for shipment, the ULD 20 is transferred to the aircraft 10 andthen loaded onto the aircraft 10 through the cargo load door 16 using aconveyor ramp, scissor lift or the like. Once inside the aircraft 10,the ULD 20 is moved within the cargo compartment 14 to a final stowedposition. Multiple ULDs may be brought on-board the aircraft 10, witheach ULD 20 being placed in a respective stowed position on the cargodeck 12. After the aircraft 10 has reached its destination, each ULD 20is unloaded from the aircraft 10 in similar fashion, generally inreverse sequence to the loading procedure. To facilitate movement of theULD 20 along the cargo deck 12, the aircraft 10 may include a cargohandling system as described herein.

Referring now to FIG. 1B, a portion of a cargo handling system 100 isillustrated, in accordance with various embodiments. In variousembodiments, the cargo handling system 100 may define a platform 101having a plurality of trays 102 supported by the cargo deck 12. Theplurality of trays 102 may be configured to support a target 21 Invarious embodiments, target 21 is a ULD (e.g., a container or a pallet)configured to hold cargo as described above with reference to ULD 20 inFIG. 1A. In various embodiments, trays 102 are disposed throughout thecargo deck 12 and may include rollers configured to facilitateconveyance of target 21 over cargo deck 12. Cargo handling system 100may further include one or more power drive units 105 and one or more ofball panel(s) 106. Ball panel(s) 106 each have a plurality of balltransfer units 107 located therein.

Cargo handling system 100 further includes one or more energy harvestingbrake system(s) 108. Energy harvesting brake systems 108 are disposed inthe platform 101. In various embodiments, the energy harvesting brakesystems 108 may be located proximate a cargo load door, such as, forexample, the cargo load door 16 described above with reference to FIG.1A, but may otherwise be located throughout the cargo handling system100 and the cargo deck 12. In various embodiments, one or more energyharvesting brake systems 108 are disposed in ball panels 106.

Referring now to FIGS. 2A and 2B, an energy harvesting brake system 108is illustrated. In accordance with various embodiments, energyharvesting brake system 108 may include a roller cylinder 200 and a tire202. Tire 202 may be located around roller cylinder 200. Tire 202 isconfigured to provide a frictional surface to engage a bottom surface ofa target, such as target 21 in FIG. 1B.

Energy harvesting brake system 108 further includes a brake stack 204, aslider disk subassembly 206, and a shaft 210. Brake stack 204, sliderdisk subassembly 206, and shaft 210 are located radially inward ofroller cylinder 200. Roller cylinder 200 is configured to rotaterelative to the shaft 210 in response to target 21, with momentaryreference to FIG. 1A, moving relative to platform 101. In variousembodiments, energy harvesting brake system 108 may further include afirst roller bearing 212 and a second roller bearing 214. First andsecond roller bearings 212, 214 may be located radially between rollercylinder 200 and shaft 210. First and second roller bearings 212, 214may be configured to facilitate the rotation of roller cylinder 200about shaft 210.

Referring now to FIGS. 3A, 3B, 3C, 3D, 3E and 3F, various illustrationsare provided to further describe the components and other aspects ofenergy harvesting brake system 108. Referring primarily to FIGS. 3A and3B, the brake stack 204 includes a nut 240, a nut retainer 242, and abiasing element 244, such as, for example, a coil spring, a Bellevillewasher, or the like. Nut 240, nut retainer 242, and biasing element 244are located proximate first roller bearing 212. In this regard, nut 240,nut retainer 242, and biasing element 244 are located axially oppositeslider disk subassembly 206. The brake stack 204 further includesnon-rotating stator plates interleaved with rotating rotor plates androller and roller cage elements located axially between each statorplate and rotor plate. For example, in various embodiments, brake stack204 may include a distal (or first) stator plate 248 configured toengage the shaft 210, a first roller and roller cage element 250, afirst rotor plate 252 configured to engage the roller cylinder 200, asecond roller and roller cage element 254, an internal (or second)stator plate 256 configured to engage the shaft 210, a third roller androller cage element 258, a second rotor plate 260, a fourth roller androller cage element 262, and a proximal (or third) stator plate 264configured to engage the shaft 210. A lock screw 298 may be used tosecure the nut 240 to the nut retainer 242. Distal stator plate 248 maybe located axially opposite proximal stator plate 264 and slider disksubassembly 206.

The stator plates act similar to stator disks and the rotor plates actsimilar to rotor disks in a friction-based brake stack. In this regard,the stator plates comprise generally non-rotating components due theirengagement with shaft 210 and the rotor plates comprise generallyrotating components due to their engagement with roller cylinder 200.For example, each of the stator plates 248, 256, 264, and the nutretainer 242 may include one or more radially inward extendingprotrusion(s) 251 configured to engage shaft 210, and each of the rotorplates 252, 260 may include one or more radially outward extendingprotrusions 284 configured to engage roller cylinder 200. Protrusions251 extend radially inward from an inner circumferential surface of thestator plate. Protrusions 284 extend radially outward from an outercircumferential surface of the rotor plate.

In various embodiments, the roller and roller cage elements are eachdisposed between opposing faces of the stator plates and the rotorplates to reduce or avoid surface contact between the opposing faces andthe wear and heat that would be otherwise generated. As illustrated,each the roller and roller cage element includes rollers 265rotationally coupled to a roller cage 266. The axis of rotation of eachroller 265 within each roller cage 266 is inclined at an angle withrespect to a radial direction (e.g., a direction perpendicular to anaxis of rotation of roller cylinder 200). In this regard, the axis ofrotation of roller 265 may be non-perpendicular to the axis of therotation of roller cylinder 200. Inclination angle of the rollers 265tends to provide a more effective braking action when an axial load isapplied to the stator and rotor plates, against an axial counter loadapplied by the biasing element 244.

In accordance with various embodiments, distal stator plate 248 and/orproximal stator plate 264 are formed of a piezoelectric material such aslead zirconate titanate, barium titanate, lithium niobate, quartz, orany other suitable piezoelectric material. In this regard, distal statorplate 248 and proximal stator plate 264 comprise piezoelectric membersof energy harvesting brake system 108. In various embodiments, distalstator plate 248 and proximal stator plate 264 each comprise apiezoelectric bimorph having a passive layer between two active layersof piezoelectric material. While distal stator plate 248 and proximalstator plate 264 are described herein as piezoelectric members, it iscontemplated and understood that brake stack 204 may include any number(i.e., more than two or fewer than two) of piezoelectric members, andthat any stator plate of brake stack 204 may be a piezoelectric member.For example, in various embodiments, internal stator plate 256 comprisea piezoelectric material.

One or more wire(s) 290 is/are in direct contact with the piezoelectricmaterial of energy harvesting brake system 108 (i.e., with distal statorplate 248 and proximal stator plate 264 of brake stack 204). In thisregard, wire 290 is electrically coupled to distal stator plate 248 andto proximal stator plate 264. In various embodiments, wire 290 may berouted through shaft 210. Stated differently, wire 290 may be located ina channel 292 defined by shaft 210.

In accordance with various embodiments, the slider disk subassembly 206includes a slider disk 268, a guide plate 270 having a plurality ofrollers 271, and a flange 272 projecting radially outward from the shaft210. Guide plate 270 is located axially between flange 272 and sliderdisk 268. The slider disk 268 is configured to remain rotationallystationary with respect to the shaft 210. For example, in variousembodiments, and with particular reference to FIGS. 3C and 3D, an innercircumferential (or radially inner) surface of the slider disk 268includes flat portions 274 that are configured to engage flat portions275 on an outer circumferential (or radially outer) surface of the shaft210. The flat portions 274 and the flat portions 275 tend to prevent theslider disk 268 from rotating with respect to the shaft 210, but permitaxial (or sliding) movement of the slider disk 268 with respect to theshaft 210 and to the flange 272.

In accordance with various embodiments, one or both of the slider disk268 and the flange 272 include peaks 276 (e.g., slider disk peaks orflange peaks, or a plurality of such peaks) and troughs 277 (e.g.,slider disk troughs or flange troughs, or a plurality of such troughs).For example, as illustrated in FIGS. 3C and 3D, the slider disk 268includes a plurality of peaks (P) interspersed with a plurality oftroughs (T) about the face (or a axial facing surface) 279 on the sliderdisk 268. In various embodiments, the plurality of peaks (P) is spacedat ninety degree (90°) intervals (e.g., at locations equal to 0°, 90°,180° and 270°). Offset by forty-five degrees (45°) with respect to thepeaks (P), the plurality of troughs (T) is also spaced at ninety degree(90°) intervals (e.g., at locations equal to 45°, 135°, 225° and 315°).In various embodiments, the surface of face 279 having the plurality ofpeaks (P) and the plurality of troughs (T) just described may define orbe characterized by a first periodic function (e.g., a sine wave)extending around the face 279 of the slider disk 268, with each peak andtrough representing, for example, a radians of the periodic function.The flange 272, as illustrated, similarly includes a plurality of peaks(P) and troughs (T) spaced at ninety degree (90°) intervals and offsetby forty-five degrees (45°) about the face (or axial facing surface) 281of the flange 272. Similar to the discussion above, the plurality ofpeaks and the plurality of troughs of the face 281 of the flange 272 maydefine or be characterized by a second periodic function extendingaround the face 281 of the flange 272. Face 279 of slider disk 268 isoriented toward face 281 of flange 272. Typically, the plurality ofpeaks (P) and the plurality of troughs (T) on both the slider disk 268and the flange 272 are in phase with each other and both the firstperiodic function and the second periodic function are substantiallyidentical or identical. Further, while the illustrated embodimentsinclude four peaks and four troughs interspersed among the peaks, thedisclosure contemplates any number of peaks and troughs, generally aneven number or both, and not necessarily arranged in the shape of a puresine wave function. In other words, the functional shape of the peaksand troughs may comprise any functional relationship (includingfunctional relationships defined, at least in part, by straight lines),so long as a plurality of peaks is interspersed with a plurality oftroughs on the face of at least one of the slider disk 268 and theflange 272.

Referring now to FIGS. 3E and 3F, guide plate 270 including rollers 271is illustrated. In various embodiments, and consistent with thedescription of the slider disk 268 and the flange 272 above, theplurality of rollers 271 includes four rollers 271 spaced at ninetydegree (90°) intervals about the guide plate 270. As illustrated inFIGS. 3A and 3B, rollers 271 are disposed at a radial location on theguide plate 270 and configured to roll over the peaks and the troughs ofthe flange 272 and the slider disk 268 as the guide plate 270 rotateswith respect to both the flange 272 and the slider disk 268. As furtherillustrated in FIGS. 3A, 3E and 3F, the guide plate 270 includes one ormore radially outward extending protrusions 278 configured to engagewith the roller cylinder 200. As a result, when the roller cylinder 200is driven (e.g., by a ULD) to rotate about the shaft 210, the guideplate 270 will rotate relative to the slider disk 268 and the flange272, both of which are held rotationally stationary with respect to theshaft 210. As the guide plate 270 so rotates, the plurality of rollers271 disposed thereon will roll up and down the peaks and troughs,respectively, thereby urging the slider disk 268 to move back and forth(i.e., toward and away) in an axial direction with respect to the flange272 of shaft 210.

Referring again to FIG. 3C and FIG. 3B, the shaft 210 further includesan elongated slot 280 (or a plurality of elongated slots) for receivingradially inward extending protrusions 251 of the stator plates 248, 256,264 and nut retainer 242. Stated differently, radially inward extendingprotrusions 251 of the stator plates 248, 256, 264 may be located inelongated slot(s) 280 defined by shaft 210. In various embodiments, theshaft 210 also includes a step face 282 to stop the nut retainer 242from sliding axially beyond the step face 282 toward the flange 272. Theshaft 210 may further include an external threaded section 283 forengaging a threaded surface of the nut 240. An end 232 and/or an 233 ofshaft 210 may comprise flat sides that correspond with a mountingstructure (e.g., a pair of lungs) configured to receive shaft 210. Theflat sides of ends 232, 233 are configured to generate an interferencewith the mounting structure, thereby preventing or reducing rotation ofshaft 210 relative to the mounting structure. One or both of the ends232, 233 of shaft 210 may define an internal threaded section 285 forreceiving a mounting pin or bolt, such as, for example, threaded pins299 in FIG. 2B. In various embodiments, and with reference to FIGS. 2Band 3B, the roller cylinder 200 includes one or more elongated slots 201configured to receive radially outward extending protrusions 284extending from rotor plates 252, 260 and radially outward extendingprotrusions 278 of the guide plate 270. Stated differently, radiallyoutward extending protrusions 284 of rotor plates 252, 260 and radiallyoutward extending protrusions 278 of the guide plate 270 may be locatedin slot 201 defined by a radially inward surface of roller cylinder 200.

Referring now to FIGS. 4A, 4B, 4C and 4D, operation of an energyharvesting brake system 108, is illustrated and described, in accordancewith various embodiments. Referring to FIG. 4A and FIG. 4B (which is aclose up view of the slider disk subassembly 206 shown in FIG. 4A), theenergy harvesting brake system 108 assumes a state of minimum, or nearminimum, brake force, where the rollers 271 mounted on guide plate 270reside in respective troughs in flange 272 and slider disk 268. In thestate of minimum brake force, the slider disk subassembly 206 assumes aminimum thickness 305. While in the state of minimum thickness, biasingelement 244 of the brake stack 204 remains substantially uncompressed(or in a state of minimum compression consistent with a defaultpre-torque or brake force), resulting in the application of a minimumbrake force against rotation of the roller cylinder 200 about the shaft210.

Referring to FIG. 4C and FIG. 4D (which is a close up view of the sliderdisk subassembly 206 shown in FIG. 4C), the energy harvesting brakesystem 108 assumes a state of maximum, or near maximum, brake force,where the rollers 271 mounted on the guide plate 270 reside onrespective peaks on flange 272 and the slider disk 268, in a fashionsimilar to that described above. In the state of maximum brake force,the slider disk subassembly 206 assumes a maximum thickness 310, whichis greater than the minimum thickness 305. While in the state of maximumthickness, the biasing element 244 of the brake stack 204 becomessubstantially compressed (or in a state of maximum compression),resulting in the application of a maximum brake force against rotationof the roller cylinder 200 about the shaft 210.

Referring to FIG. 5, the change between states of maximum force andminimum force against rotation of a roller cylinder, such as, forexample, the roller cylinder 200 of the energy harvesting brake system108 described above, is graphically illustrated in a graph 500 of brakeforce vs. degree of rotation of a roller cylinder (e.g., from 0° to360°). Two graphs appear in FIG. 5. The top graph depicts a typicalbrake roller set to a apply a constant maximum brake force 502 asdescribed in the background section above, regardless of the degree ofrotation of a corresponding roller cylinder (e.g., regardless of theposition of rotation about a 360° rotational cycle). Such an apparatusmay lead to flattening of the tire due to non-rotation for ULDs having aweight less than the weight associate with overcoming the constantmaximum brake force and to rotate the roller cylinder. The bottom graphdepicts a cyclic-brake force 504 achieved through the various energyharvesting brake system embodiments disclosed herein. As illustrated,the cyclic-brake force 504 exhibits a maximum brake force 506 that willoccur when each of a plurality of rollers on a guide plate arepositioned proximate the peaks (P) of a flange or a slider disk, asdescribed above. A minimum brake force 508, on the other hand, willoccur when each of the plurality of rollers on the guide plate arepositioned proximate the troughs (P) of the flange or the slider disk,as described above. Accordingly, and as illustrated, the cyclic-brakeforce 504 is developed through each rotation of the roller cylinder from0° to 360°. As illustrated, a default pre-torque, providing the minimumbrake force, may be built into the brake mechanism through an initialcompression of the bias element within the brake subassembly. Inaddition, it should be apparent from the graph of cyclic brake forcethat the surface of the flange or the slider disk or both is not a puresine wave, as both the peaks and the troughs have a substantially flatportion, leading, for example, to a constant maximum brake force between35° and 55° and a constant minimum brake force between 125° and 145°. Avariety of cyclic brake force profiles over a period of cyclic-brakeforce (e.g., over a period of 360° of rotation of the roller cylinder)may be achieved through variations in the faces of the flange or theslider disk or both.

In accordance with various embodiments, the piezoelectric material ofenergy harvesting brake system 108 is in operable communication with theshaft 210 and the roller cylinder 200 such that relative rotationalmotion between the shaft 210 and the roller cylinder 200 causes cyclicstress in the piezoelectric material, thereby generating electricalenergy. The cyclic-braking force generated by rotation of rollercylinder 200 deforms the piezoelectric material of to generateelectrical energy. Stated differently, the axial movement of slider disk268 during rotation of roller cylinder 200 causes a deformation of thepiezoelectric material of distal stator plate 248 and proximal statorplate 264. Stated yet another way, the piezoelectric material of distalstator plate 248 and proximal stator plate 264 deforms in response tochanges in thickness of slider disk subassembly 206. In the state ofmaximum thickness 310, the deformation of the piezoelectric material ofdistal stator plate 248 and/or proximal stator plate 264 are maximum. Inthe state of minimum thickness 305, the deformation of the piezoelectricmaterial of distal stator plate 248 and proximal stator plate 264 areminimum. In this regard, as the cyclic-brake force 504 develops througheach rotation of the roller cylinder from 0° to 360°, the piezoelectricmaterial will generate electrical energy pulse. The magnitude ofelectrical pulse generated is directly proportional to the mechanicaldeformation of the piezoelectric material of distal stator plate 248 andproximal stator plate 264

In various embodiments, the deformation energy may be converted intoelectrical energy and stored in a storage device (e.g., asupercapacitor). For example, with reference to FIG. 6, an energyharvesting system 600 including an energy harvesting brake system 108,as described above, is illustrated. The energy generated from thedeformation the piezoelectric material 602 of energy harvesting system600 (e.g., energy generated by cyclic brake force causing deformation ofdistal stator plate 248 and proximal stator plate 264) may betransferred to a voltage amplification circuit 604 of energy harvestingsystem 600 (e.g., to Villard cascade). The voltage amplification circuit604 may comprise of a series of resistors and capacitors. The voltageamplification circuit 604 may be configured to convert alternatingcurrent to direct current. The rectified and amplified voltage fromvoltage amplification circuit 604 may be stored in an energy storagedevice 606 of energy harvesting system 600. Energy storage device 606may be a battery, a supercapacitor, or any other energy storage device.In accordance with various embodiments, the energy generated by theenergy harvesting brake system 108 may be provided to components 608(e.g., sensors, lights, energy storage devices, etc.) of the cargohandling system 100 in FIG. 1B and/or of the aircraft 10 in FIG. 1A. Theenergy harvesting brake system 108 including piezoelectric material 602may thus provide a supplementary power source for the cargo handlingsystem 100 and/or for the aircraft 10.

With reference to FIG. 7, a method 700 of harvesting electrical energywhile braking is illustrated. In accordance with various embodiments,method 700 may comprise moving a target relative to a platform having anenergy harvesting brake system disposed therein (step 702) and rotatinga roller cylinder of the energy harvesting brake system with themovement of the target (step 704). Method 700 may comprises cyclicallystressing a piezoelectric material disposed in the energy harvestingbrake system with the rotation of the roller cylinder (step 706) andgenerating electrical energy with the cyclical stressing (step 708).

With combined reference to FIGS. 7, 1B and 3A, step 702 may includemoving target 21 relative to platform 101, platform 101 having an energyharvesting brake system 108 disposed therein. Step 704 may includerotating roller cylinder 200 of energy harvesting brake system 108 withthe movement of target 21. Step 706 may include cyclically stressingpiezoelectric material (e.g., distal stator plate 248 and/or proximalstator plate 264) disposed in energy harvesting brake system 108 withthe rotation of the roller cylinder 200. Step 708 may include generatingelectrical energy with the cyclical stressing of the piezoelectricmaterial

In various embodiments, method 700 may further comprise braking (e.g.,slowing or stopping) movement of the target relative to the platform(step 710). Step 710 may include braking movement of target 21 relativeto the platform 101.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment,” “an embodiment,”“various embodiments,” etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises,”“comprising,” or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

Finally, it should be understood that any of the above describedconcepts can be used alone or in combination with any or all of theother above described concepts. Although various embodiments have beendisclosed and described, one of ordinary skill in this art wouldrecognize that certain modifications would come within the scope of thisdisclosure. Accordingly, the description is not intended to beexhaustive or to limit the principles described or illustrated herein toany precise form. Many modifications and variations are possible inlight of the above teaching.

What is claimed is:
 1. An energy harvesting brake system, comprising: ashaft; a roller cylinder configured to rotate relative to the shaft inresponse to a target moving relative to a platform, the energyharvesting brake system being disposed in the platform; and apiezoelectric material in operable communication with the shaft and theroller cylinder such that relative rotational motion between the shaftand the roller cylinder causes cyclic stress in the piezoelectricmaterial thereby generating electrical energy.
 2. The energy harvestingbrake system of claim 1, further comprising: a guide plate configured torotate about the shaft, the guide plate including a roller; a sliderdisk having a first axial facing surface defining a slider disk troughand a slider disk peak, the slider disk being configured to translateaxially on the shaft in response to the roller interacting with theslider disk trough and the slider disk peak, wherein the piezoelectricmaterial is configured to deform in response to translation of theslider disk along the shaft.
 3. The energy harvesting brake system ofclaim 2, wherein the guide plate comprises a radially outward extendingprotrusion configured to engage the roller cylinder, and wherein theslider disk is rotationally stationary with respect to the shaft.
 4. Theenergy harvesting brake system of claim 3, further comprising a brakestack located around the shaft, the brake stack including a statorplate, a rotor plate, and a roller and roller cage element locatedaxially between the stator plate and the rotor plate.
 5. The energyharvesting brake system of claim 4, wherein the stator plate comprisesthe piezoelectric material.
 6. The energy harvesting brake system ofclaim 5, further comprising a flange extending radially outward from theshaft, the flange having a second axial facing surface oriented towardthe first axial facing surface, the second axial facing surface defininga flange trough and a flange peak.
 7. The energy harvesting brake systemof claim 1, further comprising a wire electrically coupled to thepiezoelectric material.
 8. The energy harvesting brake system of claim7, wherein the wire is located in a channel defined by the shaft.
 9. Theenergy harvesting brake system of claim 1, further comprising a brakestack located around the shaft, the brake stack comprising: a firststator plate and a first rotor plate, the first stator plate including afirst radially inward extending protrusion located in a first slotdefined by the shaft, the first rotor plate including a first radiallyoutward extending protrusion located in a second slot defined by theroller cylinder; a second stator plate and a second rotor plate, thesecond stator plate including a second radially inward extendingprotrusion located in the first slot defined by the shaft, the secondrotor plate including a second radially outward extending protrusionlocated in the second slot defined by the roller cylinder; a firstroller and roller cage element located axially between the first statorplate and the first rotor plate; and a second roller and roller cageelement located axially between the second stator plate and the secondrotor plate.
 10. The energy harvesting brake system of claim 9, whereinthe first stator plate comprises the piezoelectric material, and whereinthe second stator plate comprises a second piezoelectric material. 11.The energy harvesting brake system of claim 10, further comprising awire electrically coupled to the piezoelectric material and the secondpiezoelectric material, wherein the wire is located in a channel definedby the shaft.
 12. A method of harvesting electrical energy whilebraking, comprising: moving a target relative to a platform, theplatform having an energy harvesting brake system disposed therein;rotating a roller cylinder of the energy harvesting brake system withthe movement of the target; cyclically stressing a piezoelectricmaterial disposed in the energy harvesting brake system with therotation of the roller cylinder; and generating electrical energy withthe cyclically stressing the piezoelectric material.
 13. The method ofclaim 12, further comprising braking movement of the target relative tothe platform.
 14. The method of claim 12, wherein the energy harvestingbrake system, comprises: a shaft; the roller cylinder; the piezoelectricmaterial; a guide plate configured to rotate about the shaft; and aslider disk configured to translate axially on the shaft in response torotation of the guide plate about the shaft, wherein the piezoelectricmaterial is configured to deform in response to axial translation of theslider disk.
 15. An energy harvesting system, comprising: a first energystorage device; and an energy harvesting brake system electricallycoupled to the first energy storage device, the energy harvesting brakesystem including: a shaft; a roller cylinder configured to rotaterelative to the shaft; and a piezoelectric material in operablecommunication with the shaft and the roller cylinder such that relativerotational motion between the shaft and the roller cylinder causescyclic stress in the piezoelectric material thereby generatingelectrical energy.
 16. The energy harvesting system of claim 15, whereinthe energy harvesting brake system further comprises: a guide plateconfigured to rotate about the shaft; a slider disk configured totranslate axially on the shaft in response to rotation of the guideplate about the shaft, wherein the piezoelectric material is configuredto deform in response to axial translation of the slider disk.
 17. Theenergy harvesting system of claim 15, further comprising a voltageamplification circuit electrically coupled between the piezoelectricmaterial and the first energy storage device.
 18. The energy harvestingsystem of claim 17, further comprising a cargo handling componentconfigured to receive electrical energy from the first energy storagedevice.
 19. The energy harvesting system of claim 18, wherein the cargohandling component comprises at least one of a sensor, a light, or asecond energy storage device.
 20. The energy harvesting system of claim19, wherein the energy harvesting brake system further comprises aflange extending radially outward from the shaft, the flange having anaxial facing surface defining a flange trough and a flange peak.